These types are called heart stents, but they're also referred to as cardiac stents or coronary stents. Usually made of metal mesh, they’re put into arteries in a procedure called a percutaneous coronary intervention or, its more common name, angioplasty.

Performed with local anesthesia and mild sedation, angioplasty involves no major incisions and usually takes about an hour. If you need more than one stent, it can take longer.

Compared to coronary artery bypass surgery, which is much more invasive, people who get stents have less discomfort and a shorter recovery time.

But stenting isn't risk-free. A blood clot can form in one and cause your arteries to narrow again suddenly. It may even cause a complete blockage. To prevent this, people take one or more blood-thinning drugs after they get a stent. These can include aspirin, which usually must be taken indefinitely, and clopidogrel (Plavix), prasugrel (Effient), or ticagrelor (Brilinta), which are usually prescribed for at least 1 and up to 12 months.

Scar tissue or plaque can also form in the area of your stent. This can cause your artery to narrow again over a period of months. Your doctor may call this restenosis. If it happens, another stent can often solve the problem. In some cases, coronary artery bypass surgery may be needed.

Why We Have Them

In the late 1970s, doctors began using balloon angioplasty to treat coronary arteries that got too narrow.

A very thin, long, balloon-tipped tube, called a catheter, is put into an artery in either the groin or arm. It’s then moved to the blockage with help from an X-ray. Once it’s there, the balloon at the tip of the catheter is inflated to compress the blockage and get blood flow going. Then it’s deflated to allow the whole thing to be removed.

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Because no new support is left, in a small percentage of cases, the artery will regain its previous shape or even collapse after the balloon is deflated. About 30% of coronary arteries treated with balloon angioplasty get narrower again.

To help solve these problems, small stents were created that could be mounted on the balloon and put into a blood vessel. The stent expands when the balloon is inflated, locks into place, and forms a permanent scaffold to hold the artery open after the balloon is deflated and removed.

In 1986, French researchers implanted the first stent into a human coronary artery. Eight years later, the FDA approved the first heart stent for use in the U.S.

Types

First-generation stents were made of bare metal. Although they almost eliminated the risk of the artery collapsing, they only modestly reduced the risk of re-narrowing. About a quarter of all coronary arteries treated with bare-metal stents would close up again, usually in about 6 months.

So doctors and companies began testing stents coated with drugs that interrupted the re-narrowing. These are called drug-eluting stents.

In clinical trials, these reduced re-narrowing cases to less than 10%. They also lowered the need for repeat procedures for people with diabetes, who have a bigger chance of their arteries getting narrow again.

Still, there were concerns that drug-eluting stents were associated with a rare but serious complication called in-stent thrombosis. This is where a blood clot forms in a stent one or more years after it's implanted.

Because this complication can be fatal, it’s important that people with drug-eluting stents take aspirin and an anticlotting drug as prescribed until a doctor tells them to stop.

Innovations

In 2016, the FDA approved a new type of stent made of a special polymer that eventually dissolves into the body. This new stent releases a drug called everolimus, which limits the growth of scar tissue that can re-block the coronary artery.

The global market for coronary stents is projected to increase to $5.6 billion by 2020, the consulting firm GlobalData says.

Many new second- and third-generation stent designs are being developed, in clinical trials, or have been approved for use outside the U.S. These include:

One with a covering that delivers an anti-restenosis drug for months and then basically becomes a bare-metal stent

A version that is absorbed by the body and disappears after it has done its work

A stent that uses a coating to quickly create a thin, all-natural layer inside the artery